1. Field of the Invention
Embodiments of the present invention are directed to creation of therapeutic gas, possibly for delivery to a patient for respiratory use. More particularly, embodiments of the invention are directed to systems for creation of therapeutic gas for delivery to a patient and for filling portable cylinders for ambulatory use.
2. Background of the Invention
Many patients with lung and/or cardiovascular problems may be required to breathe therapeutic gas in order to obtain sufficient dissolved oxygen in their blood stream. So that these patients may be ambulatory, therapeutic gas may be delivered from a portable cylinder. A portable cylinder may, however, provide only limited volume, and therefore will periodically need to be refilled. While it is possible to have these cylinders exchanged or refilled by way of commercial home health care services, some patients have systems within their homes which perform a dual function: filling portable cylinders with oxygen therapeutic gas; and providing therapeutic gas to the patient for breathing. Systems such as these have come to be known as “trans-fill” systems.
U.S. Pat. No. 5,858,062 to McCulloh et al. (assigned to Litton Systems, Inc., and thus hereinafter the “Litton patent”) may disclose a system where atmospheric air may be applied to a pressure swing absorption (PSA) system which removes nitrogen from the air and thereby increases the oxygen content, e.g to approximately 90% or above. In the Litton patent, oxygen-enriched gas exiting the PSA system may couple to a patient outlet and a pressure intensifier. The pressure of enriched gas supplied by the PSA system may be regulated (in this case lowered) before being provided to a patient. Likewise, the pressure of the enriched gas from the PSA system may be increased by the intensifier for filling the cylinder. Thus, in the Litton patent, the enriched gas product of the PSA system is separated into two streams (outlets in the terminology of the Litton patent) each having the same pressure. The Litton patent may also disclose the use of an oxygen sensor to monitor the enriched gas exiting the PSA system. However, the Litton patent discloses only monitoring oxygen content of the enriched gas exiting the PSA system, and situations where the oxygen content may be correct but the enriched gas product contains other harmful chemicals and/or gases may not be detected.
U.S. Pat. No. 6,393,802 to Bowser et al. (hereinafter the “Dowser patent”) may disclose an oxygen concentrator that is adapted to supply therapeutic gas to the patient and/or to a cylinder filler, which cylinder filler is controlled to automatically fill a portable cylinder. Much like the Litton patent, the Bowser patent discloses an enriched gas product from an oxygen concentrator split into a first stream provided to a compressor (which may then be provided to fill a cylinder), and a second stream provided to a patient (possibly after proceeding through a flow regulator). The Bowser patent also discloses that prior to filling a cylinder, the gas pressure of the portable cylinder should be measured. If the gas pressure of the portable cylinder is below a predetermined safe minimum, the cylinder is not filled. The Bowser patent indicates this may be desirable because a cylinder having very little residual gas pressure may have been left open and the interior of the cylinder may have become contaminated.
U.S. Pat. No. 6,446,630 to Todd, Jr. (hereinafter the “Todd patent”) may disclose a system where an enriched gas stream exiting an oxygen concentrator is selectively delivered to a patient (at least during a portion of the patient's inhalation) and the remainder of the time delivered to a cylinder filler. The Todd patent also mentions the use of an oxygen sensor to test the enriched gas from the oxygen concentrator provided to the patient, but fails to discuss the possibility that while oxygen concentration levels may be correct, other, harmful, gases may be present.
Thus, what is needed in the art is a method and related system that more closely monitors the therapeutic gas. Further, what is needed is a method and related system that more efficiently provides the therapeutic gas to a patient.